Blar i forfatter "Romashkin, Alexander E."

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    • Chromium evidence for protracted oxygenation during the Paleoproterozoic 

      Mänd, Kaarel; Planavsky, Noah J.; Porter, Susannah M.; Robbins, Leslie J.; Wang, Changle; Kreitsmann, Timmu; Paiste, Kärt; Paiste, Päärn; Romashkin, Alexander E.; Deines, Yulia E.; Kirsimäe, Kalle; Lepland, Aivo; Konhauser, Kurt O. (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-24)
      It has commonly been proposed that the development of complex life is tied to increases in atmospheric oxygenation. However, there is a conspicuous gap in time between the oxygenation of the atmosphere 2.4 billion years ago (Ga) and the first widely-accepted fossil evidence for complex eukaryotic cells . At present the gap could either represent poor sampling, poor preservation, and/or difficulties ...

    • Identifying global vs. basinal controls on Paleoproterozoic organic carbon and sulfur isotope records 

      Paiste, Kärt; Lepland, Aivo; Zerkle, Aubrey L.; Kirsimae, Kalle; Kreitsmann, Timmu; Mänd, Kaarel; Romashkin, Alexander E.; Rychanchik, Dimitry V.; Prave, Anthony R (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-03)
      Paleoproterozoic sedimentary successions are important archives of the redox evolution of Earth’s atmosphere and oceans. Efforts to unravel the dynamics of our planet’s early oxygenation from this archive rely on various geochemical proxies, including stable carbon and sulfur isotopes. However, ancient metasedimentary rocks often experienced early- and late-stage (bio)geochemical processes making ...

    • Iron Isotopes Reveal a Benthic Iron Shuttle in the Palaeoproterozoic Zaonega Formation: Basinal Restriction, Euxinia, and the Effect on Global Palaeoredox Proxies 

      Mänd, Kaarel; Lalonde, Stefan V.; Paiste, Kärt; Thoby, Marie; Lumiste, Kaarel; Robbins, Leslie J.; Kreitsmann, Timmu; Romashkin, Alexander E.; Kirsimäe, Kalle; Lepland, Aivo; Konhauser, Kurt O. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-03-31)
      The Zaonega Formation in northwest Russia (~2.0 billion years old) is amongst the most complete successions that record the middle of the Palaeoproterozoic era. As such, geochemical data from the formation have played a central role in framing the debate over redox dynamics in the aftermath of the Great Oxidation Event (GOE). However, uncertainty over local redox conditions and the degree of ...

    • The kaolinite shuttle links the Great Oxidation and Lomagundi events 

      Hao, Weiduo; Mänd, Kaarel; Li, Yuhao; Alessi, Daniel S.; Somelar, Peeter; Moussavou, Mathieu; Romashkin, Alexander E.; Lepland, Aivo; Kirsimäe, Kalle; Planavsky, Noah J.; Konhauser, Kurt O. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-19)
      The ~2.22–2.06 Ga Lomagundi Event was the longest positive carbon isotope excursion in Earth’s history and is commonly interpreted to reflect perturbations in continental weathering and the phosphorous cycle. Previous models have focused on mechanisms of increasing phosphorous solubilization during weathering without focusing on transport to the oceans and its dispersion in seawater. Building from ...

    • Multiple sulphur isotope records tracking basinal and global processes in the 1.98 Ga Zaonega Formation, NW Russia 

      Paiste, Kärt; Lepland, Aivo; Zerkle, A.L.; Kirsimäe, Kalle; Izon, G.; Patel, N.K.; McLean, F.; Kreitsmann, T.; Mänd, Kaarel; Bui, T.H.; Romashkin, Alexander E.; Rychanchik, Dimitry V.; Prave, Anthony R (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-09-19)
      The exceptionally organic-rich rocks of the 1.98 Ga Zaonega Formation deposited in the Onega Basin, NW Russia, have refined our understanding of Earth System evolution during the Paleoproterozoic rise in atmospheric oxygen. These rocks were formed in vent- or seep influenced settings contemporaneous with voluminous mafic volcanism and contain strongly <sup>13</sup>C-depleted organic matter. ...